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Ecdyonurus venosus (False March brown)

Nymphs of Ecdyonurus venosus are typically found in riffle areas of rivers and streams.  They are usually found clinging to submerged plants and stones, although they may swim if disturbed.  E. venosus feeds either by scraping periphyton from the substrate or by gathering fine particulate organic detritus from the sediment.  There is one generation a year, which usually overwinters as nymphs and emerges between April and July, and often as late as September or October.

 


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Emergence of the adults takes place at the surface of the water and often continues well into dusk.  The males of this species can be found swarming throughout the day.  Once mated, the female either flies upstream and descends to the surface of the water to release a few eggs by dipping the tip of her abdomen on to the surface at intervals, or by resting on a stone above the water and laying her eggs on the river bed by dipping her abdomen below the surface.    After several visits to the water the egg supply of up to 6000 eggs is finished and the spent female falls on to the surface.

 

Due to the problems with identification of nymphs, it is difficult to compile a complete distribution for this species.  E. venosus is however, thought to occur in suitable habitats throughout the UK and Ireland.